The egg would firm the mix up. In a typical 'banger' I would use 77% Meat, 13% Water, 8% Rusk and 2% seasoning or thereabouts. It's not prescriptive. Many commercial sausages a have far more filler, and some people prefer a lot less.

For me, it's not about the economics. It's that,without the rusk, the sausage just doesn't have the characteristics to be a classic British sausage.

Thanks Wheels, and DanMcG for your time and trouble to answer. Next time I will recalculate this one. I definitely tasted it when first bite, but it disappears in the remaining flavors as the lunch progresses.